A generic injection section is disclosed in PCT/EP2014/072554 (date of application Oct. 21, 2014). The injection section comprises a channel for conducting an exhaust gas flow and an injector connection arranged laterally on the channel, to which an injector for introducing a fluid, that is a liquid or a gas, into the exhaust gas flow, can be connected. Furthermore, an injection chamber is formed in the channel in the region of the injector connection, which on the one hand is delimited by a first separating wall which with respect to the exhaust gas flow is arranged in the channel upstream of the injector connection, which is perforated and through which exhaust gas can flow and on the other hand by a second separating wall which with respect to the exhaust gas flow is arranged in the channel downstream of the injector connection, which is perforated and through which exhaust gas can flow. With this injector section, a perforation of the first separating wall is configured so that when the first separating wall is subjected to a through-flow, it creates at least two exhaust gas part flows within the injection chamber, which form two opposing flow vortices. Furthermore, through the configuration of the perforation of the first separating wall it is achieved that both the exhaust gas partial flows flow separately proximally with respect to a channel wall laterally delimiting the injection chamber and flow jointly distally with respect to the channel wall. Intensive swirling within the injection chamber is thereby achieved. At the same time, a comparatively long dwell time for the exhaust gas within the injection chamber is achieved. An improved mixing-through, between exhaust gas and introduced liquid or introduced gas, can thereby be achieved. Provided a liquid is introduced, improved evaporation of the liquid can be additionally achieved through this measure.
WO 2010/146285 A1 discloses an exhaust gas aftertreatment device in the form of an SCR-system, SCR standing for selective catalytic reduction. The SCR-system comprises a tubular housing for conducting an exhaust gas flow, which in an outlet section contains an SCR-catalytic converter. The housing additionally comprises an inlet section, which with respect to the exhaust gas flow is arranged upstream of the outlet section and which contains an oxidation catalytic converter. Axially between the inlet section and the outlet section an injection section is arranged, wherein a further housing section that is integrally formed on the inlet section, defines a channel of the injection section which likewise serves for conducting the exhaust gas flow. In the injection section, an injector connection is laterally arranged on the channel on which an injector for laterally injecting or introducing, via a nozzle, a liquid or of a gas in the exhaust gas flow is connected. In the channel of the injection chamber, an injection chamber is formed in the region of the injector connection which on the one hand is delimited by a first separating wall which with respect to the exhaust gas flow is arranged in the channel upstream of the injector connection and which is perforated and through which exhaust gas can flow and on the other hand by a second separating wall which with respect to the exhaust gas flow is arranged in the channel downstream of the injector connection and which is perforated and through which exhaust gas can flow. With the SCR-system, the two separating walls are configured or formed in conjunction with their perforations so that during the operation of the exhaust system a spin or vortex or rotational flow is formed, in the case of which the entire exhaust gas flow rotates about the longitudinal center axis of the channel. Because of this it is achieved that a flow path in the injection chamber, which the exhaust gas flow follows from the perforation of the first separating wall to the perforation of the second separating wall, is by at least 20% longer than an axial distance between inlet section and outlet section. A mixing section is thus created, in which an injected liquid can evaporate and become mixed-through with the exhaust gas flow.
In the case of an SCR-system, the injected liquid is a reduction agent. Preferably, a watery urea solution, which is ultimately converted into ammonia and carbon dioxide by means of thermolysis and hydrolysis is currently preferred in order to convert nitrogen oxides deposited in the SCR-catalytic converter into nitrogen and water. Of decisive importance for the efficiency of such an SCR-system on the one hand is as complete as possible an evaporation of the reduction agent introduced in liquid form. On the other hand, as intensive as possible a mixing-through of the evaporated reduction agent with the exhaust gas flow also has to be achieved.
Alternatively, with modern SCR-systems, a gaseous reduction agent can also be atomised-in, which for example is gaseous ammonia. Storage in this case can take place in the form of solids, which are evaporated for example by means of electrically supplied heat in order to generate the gaseous ammonia. In the case of these so-called Amminex systems, the ammonia is thus directly available in the exhaust gas flow so that intensive mixing-through with the exhaust gas flow is merely required since the evaporation already takes place in advance, outside the exhaust gas flow.